<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=scr, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        //能返回值的语句叫做表达式
        var a = 1;
        var b = 2;
        var c = 3;
        var d = 4;

        var z = a,b,c,d;//,b相当于是重新定义，上边b已经定义了
        console.log(z);//打印1
        var z = (a,b,c,d);
        console.log(z);//打印4



        //关于逻辑与
        const e = 'abc';
        const f = 'xyz';

        console.log(e&&f);//输出xyz
    </script>
</body>
</html>